Hydraulic impact mechanism

Abstract

A hydraulic impact mechanism includes a housing with a cylinder bore, a forward working chamber and a rear working chamber, a hydraulic fluid supply passage connected to the forward working chamber and a drain passage connected to the rear working chamber, a hammer piston reciprocally guided in the cylinder bore for delivering blows to a working implement attached to the housing, a pressure accumulator pre-loaded to a certain pressure level, and a distribution valve for alternatingly connecting the rear working chamber to the supply passage and the drain passage to thereby reciprocate the hammer piston, wherein a sequence valve is provided in the drain passage to keep up the pressure in the rear working chamber so that the resulting forward directed force prevents the piston from being moved backwards in the cylinder bore at pressure levels in the supply passage below the pre-load pressure level of the accumulator.

1. A hydraulic impact mechanism comprising:
 a housing having a hydraulic fluid supply passage, a drain passage, and a cylinder bore including a forward working chamber continuously communicating with the supply passage and a rear working chamber; 
 a hammer piston reciprocally guided in the cylinder bore; 
 a pressure accumulator pre-loaded to a certain pressure level and communicating with the forward working chamber; 
 a distribution valve which is arranged to alternatingly connect the rear working chamber to the supply passage and to the drain passage; 
 a sequence valve provided in the drain passage, said sequence valve having an opening pressure which is adapted to keep up the pressure in the rear working chamber to a level where a resulting force on the hammer piston prevents the hammer piston from moving rearwards at pressure levels in the supply passage below the pre-load pressure level of the accumulator. 
 
   
   
     2. The impact mechanism according to  claim 1 , comprising a central drain chamber arranged between said cylinder bore and the piston, said central drain chamber being arranged to provide a control pressure to said distribution valve and having an outlet passage connected to the drain passage upstream of said sequence valve. 
   
   
     3. The impact mechanism according to  claim 1 , comprising a central drain chamber arranged between said cylinder bore and the piston, said central drain chamber being arranged to provide a control pressure to said distribution valve and having an outlet passage connected to the drain passage downstream of said sequence valve.